This application relates generally to inspecting objects, and more specifically to methods and apparatus for generating a mask for use with inspecting an object.
Objects are sometimes inspected, for example, to determine a size and/or shape of all or a portion of the object and/or to detect defects in the object. For example, some gas turbine engine components, such as turbine or compressor blades, are inspected to detect fatigue cracks that may be caused by vibratory, mechanical, and/or thermal stresses induced to the engine. Moreover, and for example, some gas turbine engine blades are inspected for deformations such as platform orientation, contour cross-section, bow and twist along a stacking axis, thickness, and/or chord length at given cross-sections. Over time, continued operation of the object with one or more defects may reduce performance of the object and/or lead to object failures, for example, as cracks propagate through the object. Accordingly, detecting defects of the object as early as possible may facilitate increasing the performance of the object and/or reducing object failures.
To facilitate inspecting objects, at least some objects are inspected using a light measurement system that projects a structured light pattern onto the surface of the object. The light measurement system receives the structured light pattern reflected from the surface of the object and then analyzes the deformation of the reflected light pattern to calculate the surface features of the object. More specifically, during operation, the object to be inspected is sometimes coupled to a test fixture and positioned proximate to the light measurement system. A light source is then activated such that the emitted light illuminates the object. However, during operation, the light source may also illuminate at least a portion of the test fixture and/or portions of the object outside an area to be inspected, which may create inter-reflections between the object and the test fixture, and/or between an area of the object to be inspected and portions of the object outside the area to be inspected. For example, inter-reflections may be caused if the test fixture has a shape or finish that casts reflections on the object, or if the object has a relatively mirror-like finish that reflects an image of the test fixture. Such inter-reflections may result in reduced image quality and poor measurement results, possibly leading to an incorrect interpretation of surface features of the object.
Accordingly, at least one known imaging system includes a mask that is formed using duct tape for example. More specifically, duct tape is attached to the light source to facilitate reducing inter-reflections. However, the duct tape mask generally is attached to the light source in a geometric pattern that does not effectively shield the fixture from the object. Therefore, inter-reflections between the test fixture and the object, and/or between an area of the object to be inspected and portions of the object outside the area to be inspected may still be generated.